The ruling lets unions keep collecting fees from nonunion members -- for now. The case is likely to be retried.

The U.S. Supreme Court on Tuesday left unsettled one of the most important cases involving public-sector workers in decades.

In Friedrichs v. California Teachers Association, a group of teachers had argued that requiring nonmembers to pay fees for the cost of negotiating contracts was unconstitutional and in violation of their free speech rights. But in a 4-4 decision on Tuesday, the nation's highest court left intact a prior appeals court ruling permitting government unions to collect the fees.

Although the one-sentence opinion affirmed the lower court's ruling, it set no legal precedent. It's expected that the court could soon revisit the ruling, raising the possibility that the union’s victory may be short-lived.

Union leaders hailed the decision, calling the case an attempt to weaken collective bargaining and suppress their political influence.

“In Friedrichs, the court saw through the political attacks on the workplace rights of teachers, educators and other public employees," said Lily Eskelsen García, president of the National Education Association, in a statement. "This decision recognizes that stripping public employees of their voices in the workplace is not what our country needs."

Lawyers with the Center for Individual Rights, a conservative legal group representing the plaintiffs, vowed to fight the ruling. The center’s president, Terry Pell, said the firm would file a petition for the court to revisit the case.

“Either compulsory dues are an acceptable exception to the First Amendment or they are not," said Pell. "A full court needs to decide this question and we expect this case will be reheard when a new justice is confirmed."

In a 1977 decision, the court ruled that public unions could require workers (even if they aren't dues-paying members) to cover the cost of negotiating contracts with what's known as “fair share fees” or “agency fees." Separate fees, which members can opt out of paying, fund unions’ political activities. The plaintiffs in Friedrichs, however, argued that all union activity is inherently political, so states shouldn’t require public employees to contribute to costs of negotiating contracts either. Labor advocates contend that this would lead to “free riders” benefiting from union representation without sharing the costs of negotiating contracts.

Earlier this year, court observers had expected a 5-4 ruling that would have overturned the decades-old precedent on the issue. But the sudden death of Justice Antonin Scalia, whose line of questioning seemed to suggest he opposed the unions, altered the dynamics of the court.

President Obama nominated federal Court of Appeals Judge Merrick B. Garland to fill the vacancy on the court, but Senate Republican leaders have pledged to not consider his nomination until after the November elections.

Eliminating requirements for union workers to cover the costs of labor negotiations would deal a blow to labor unions’ operating revenues. It’s difficult to say how much union coffers would take a hit, though, as the extent to which they rely on fair share fees varies. California Teachers Association members pay about $1,000 in annual dues, of which roughly $600 to $650 covers fair share fees for representation.

Union members additionally pay separate fees that fund lobbying and political activities but have the right to opt out of paying such fees. The Friedrichs case called into question whether workers should have to opt out in the first place, with the plaintiffs arguing union workers should instead opt in before paying any lobbying fees. With the 4-4 tie, union members can continue to opt out of (not into) paying such fees. Any changes relating to the collection of these fees are likely to be felt more over the longer term. It’s believed that most longtime union members aren’t likely to opt out of paying these costs, but more new members taking their place might not elect to opt in if required to do so.

More than half of states have passed right-to-work laws, prohibiting unions from requiring employees to join or pay dues. Particularly in those states, any future court decision carries major implications for millions of public employees. In right-to-work states, overall union membership rates are typically lower.

The public sector represents one of the last remaining strongholds of the U.S. labor movement. Nationally, more than a third of all public employees belong to unions, compared to less than 7 percent of private-sector workers, according to the most recent Labor Department estimates.

*This story has been updated from the version that ran in the April print magazine to reflect the U.S. Supreme Court's ruling.